execute

# File lib/rubygems/commands/help_command.rb, line 98
  def execute
    command_manager = Gem::CommandManager.instance
    arg = options[:args][0]

    if begins? "commands", arg then
      out = []
      out << "GEM commands are:"
      out << nil

      margin_width = 4

      desc_width = command_manager.command_names.map { |n| n.size }.max + 4

      summary_width = 80 - margin_width - desc_width
      wrap_indent = ' ' * (margin_width + desc_width)
      format = "#{' ' * margin_width}%-#{desc_width}s%s"

      command_manager.command_names.each do |cmd_name|
        summary = command_manager[cmd_name].summary
        summary = wrap(summary, summary_width).split "\n"
        out << sprintf(format, cmd_name, summary.shift)
        until summary.empty? do
          out << "#{wrap_indent}#{summary.shift}"
        end
      end

      out << nil
      out << "For help on a particular command, use 'gem help COMMAND'."
      out << nil
      out << "Commands may be abbreviated, so long as they are unambiguous."
      out << "e.g. 'gem i rake' is short for 'gem install rake'."

      say out.join("\n")

    elsif begins? "options", arg then
      say Gem::Command::HELP

    elsif begins? "examples", arg then
      say EXAMPLES

    elsif begins? "platforms", arg then
      say PLATFORMS

    elsif options[:help] then
      command = command_manager[options[:help]]
      if command
        # help with provided command
        command.invoke("--help")
      else
        alert_error "Unknown command #{options[:help]}.  Try 'gem help commands'"
      end

    elsif arg then
      possibilities = command_manager.find_command_possibilities(arg.downcase)
      if possibilities.size == 1
        command = command_manager[possibilities.first]
        command.invoke("--help")
      elsif possibilities.size > 1
        alert_warning "Ambiguous command #{arg} (#{possibilities.join(', ')})"
      else
        alert_warning "Unknown command #{arg}. Try gem help commands"
      end

    else
      say Gem::Command::HELP
    end
  end